Types of FurnacesAbout Home Renovations has an article devoted to the three types of gas furnaces. Here is a summary:
- Single Stage Furnace: Turns on or off. "On" is the highest flame setting.
- Double Stage Furnace: Turns on to either high or low flame setting. It also turns off.
- Modulating Furnace: The flame increases or decreases incrementally so that room temperature never varies more than 1 or 2 degrees from the thermostat's target temperature.
1. General OperationWhen the modulating furnace is initially called into action--for example, first thing in the morning--it begins at the highest flame and blower level possible. Thus, it sounds and feels very much like single-stage gas furnaces you have experienced before.
That is where the difference ends. Once enough heat has built up in the house, there is no more need for a huge influx of heat from the furnace, at least for awhile.
After that, you will hear and feel the modulating furnace turn on and off frequently--far more frequently than with single-stage furnaces--but at lower levels.
The modulating furnace is basically pushing lesser amounts of heat into your house, but on a more frequent basis.
It is a unique experience to feel heat coming in, without the usual accompanying swoosh of a blower at full capacity.
2. ComfortComfort is the marked, immediate change that I have noticed. Because the furnace does not wait for room temperature to drop dramatically before kicking on, you feel a more consistent room temperature yourself.
The house never really feels hot or cold. If you've got the thermostat set to your desired temperature, the house feels just right. You do need to have a well-insulated house, though.
3. NoiseIs it modulating furnaces in general? Is it my particular brand?
I am not sure yet. But this modulating furnace operating at full capacity is as noisy as a 747 taking off. Naturally, all modulating furnace manufacturers advertise their units as being "whisper-quiet."
Plus, the noise has a churning effect, almost like the blower motor is laboring to push out the air.
One thing to keep in mind with any new furnace purchase is that air is most likely coming through your vents at a higher volume. So, you'll hear more whooshing from the vents.
But the furnace itself?
4. CostPurchasing a modulating gas furnace is done purely on faith. You're told that modulating furnaces have an AFUE energy efficiency rating of 80%-98% You read that you can reap big tax credits for buying these furnaces.
But they can be sickeningly expensive. Expect to pay $4,000 to $5,000 for a 98% AFUE furnace, installed.
You won't recoup that cost in the first winter, not even close. Or the second or third. Modulating furnaces are a long-term purchases where you expect to be in the house for ten years or more. Because I have not owned this modulating furnace long enough, I have nothing to say at this time about its energy efficiency and cost savings.
5. Resale ValueHigh efficiency, modulating gas furnaces are eco-friendly, green purchases. Yet the resale value of green home improvements still remain debatable.
Theoretically, a better furnace should add value to your home upon sale. In practice, I have found--both as a buyer and seller of homes--that furnace age and general condition are the main points. You could mention your high-efficiency furnace in your sales literature, but I am not sure you will see a much higher sales price because of it.